The present invention relates to a deformable mirror. More particularly, the present invention relates to deformable mirrors for use in adaptive and active optical systems for use in optical technology laser communication directed energy systems.
Adaptive and active optical elements are designed to improve optical system performance in the presence of phase aberrations. An ideal deformable mirror should have sufficient frequency bandwidth for compensation of fast changing wave front aberrations induced by either atmospheric turbulences or by turbulent air flows surrounding flying objects. Applications such as atmospheric target tracking, remote sensing from flying aircraft, boundary layer imaging, laser communication and laser beam projection over near horizontal propagation paths a phase aberration frequency bandwidth can exceed several kHz. Compensating for fast changes has typically been done using small deformable mirrors. These mirrors are usually a few inches or less in overall size. An example of such a mirror is the micro-electro-mechanical systems (MEMS) based deformable mirrors, other examples include piezoelectric deformable mirrors based on semi-active or passive bimorph elements (also commonly referred to as bimorph mirrors), or deformable mirrors with an array of push-pull type actuators are also well known in the art.
All of the aforementioned deformable mirror systems and devices suffer from scalability problems. These mirror systems are all difficult or impractical to scale up to a larger size without either significant reduction of their operational speed or substantial increase of optical system complexity. Increases in complexity usually translate into additional costs and physically larger devices. Complexity and size are two common issues that are encountered when attempting to scale up deformable mirrors by aggregating or combining a plurality of small deformable mirrors into one large phased array.
The problems outlined above are more clearly understood from the following discussion. To match the small size of a deformable mirror whose diameter is “d”, the optical telescope aperture where diameter D>>d, must be re-imaged with a demagnification factor M=D/d. Additionally, in most practical applications the demagnification factor M can be extremely large (on the order of 100 or even more). Hence, re-imaging of the telescope pupil with a high magnification factor requires installation of additional optical elements including one or more optical relay systems. This results in a substantial increase of complexity, size, weight, and cost of the entire optical device or system. The high magnification factor introduces others problems including that of additional vibration and higher temperature. Generally, deformable mirror systems alone are highly sensitive to vibrations and high-thermal gradient environmental factors, adding additional complexity to these devices tends to have an adverse effect them.
Clearly there is a need in the art for a deformable mirror that is scalable, able to perform many deformation cycles at high rate of speed, and is not overly complex. We believe that the present invention addresses these needs.